Apparatus for determining the condition of ionized fluids



Jan. 29, 1957 D. R. DE BOISBLANC 2,779,917

APPARATUS FOR DETERMINING THE CONDITION OF IONIZED FLUIDS Filed April14, 1952 "Q" METER I :3 13 E 2| I 26 F L I91 2a 3o SQUARING .1.-

AMPLIFIER CIRCUIT OSCILLATOR INVENTOR. D. R. DE BOISBLANC APPARATUS FORDETERMINING THE CONDI- TION F IONIZED FLUIDS Deslonde R. de Boisblanc,Idaho Falls, Idaho, assignor to Phillips Petroleum Company, acorporation of Delaware Application April 14, 1952, Serial No. 282,094

12 Claims. (Cl. 324-40) This invention relates to apparatus fordetermining the condition of ionized fluids. In another aspect, itrelates to apparatus for measuring the temperature of ionized fluids.

When a coil of wire is immersed in a medium containing free ions orelectrons, such as an electrolyte or thermally ionized gas, the movementof the ions induces voltages in the coil. Where such motion is caused bythe Brownian agitation, which is a function of temperature, the voltagesare of a random nature and the energy contained in any portion of thefrequency spectrum is simply related to the absolute temperature. Viewedfrom the terminals of the coil, this voltage is indistinguishable fromthermal noise which would arise if the coil had a series resistance. Thenoise power appearing at the coil terminals is:

E =a (4RkTdf) 1 where R is the value of the series resistance, k isBoltzmanns constant, T is the absolute temperature, d is the interval offrequency over which measurements are made,

If the coil is placed in a conducting medium, at any frequency, the coilexhibits a resistance indistinguishable from the simple seriesresistance mentioned above. Furthermore, from the standpoint of athermal noise generator, the equivalent noise temperature is that of themedium, not that of the coil. It will be understood that the effect ofambient temperature on the noise output of the coil is masked while theionized fiuit is at a substantially higher temperature than ambienttemperature. If the efiect of ambient temperature is not so masked, itcan be readily compensated for, as those skilled in the art willunderstand. The effect of excitation of the coil is to cause it toindicate a higher temperature than the correct value, but since theenergies in such transitions are predominantly electrostatic, thecoefiicient of coupling with the coil is very small compared to that ofthe thermally moving ions.

In carrying out the invention, an inductance coil is wrapped around avessel in which the ionizedfluid is contained. Suitable components areassociated with this coil as to provide a tuned circuit. The output ofthe coil is a function of the velocity of ion movement and, hence, ofthe temperature of the fluid. After suitable calibration, the quadraticoutput of the coil directly indicates the temperature. In anotherembodiment, a second tuned circuit is provided, the Q of which can bevaried, for example, by adjustment of a resistance connected in StatesPatent 0 series with the coil. The noise power appearing in the coilterminals of the second coil is as follows:

E =a '(r'R'k'T'df') (3 where the symbols are as identified in connectionwith Equation 1, except that T is the temperature of the second coilitself.

In accordance with the invention, under the operating conditions, the Qof the second circuit is so adjusted as to equal the Q of the circuitincluding the coil surrounding the gas-containing vessel. As a result,the factors a in the two equations become equal and the followingrelationship exists between the electrical noise powers appearing at theterminals of the respective coils.

By incorporating a circuit whose output is the square of the inputvoltage, the circuit can be calibrated so that the temperature of theionized fluid is directly determined.

It is an object of the invention to provide improved apparatus forindicating the condition of ionized fluids.

It is a further object to provide an improved circuit for determiningthe temperature of ionized fluids.

Various other objects, advantages and features of the invention willbecome apparent from the following detailed description taken inconjunction with the accompanying drawing, in which the figure is aschematic circuit diagram illustrating a preferred application of theinvention.

Referring now to the drawing, I have shown a container 10 encircled byan inductance coil 11, the container holding an ionized gas, thetemperature of which is to be determined. In some variations of theinvention, the container 10 can define a zone in which flame isperiodically present.

The coil 11 is connected in a tuned circuit 12 including a fixedresistance 13 of small ohmic value connected in series with the coil anda condenser 14 connected in parallel with the coil-resistancecombination. The Q of the circuit can be measured by a meter 15 which isshown as being connected across the coil terminals. A suitable meter ofthis type is shown in an article entitled The Measurement of Q,Electronic Engineering, April 1943, pages 452 ff.

A reference tuned circuit is constituted by a coil 16 which hasconnected in series therewith, an adjustable resistance 17 and a fixedresistance 18, a condenser 19 being connected in parallel with theinductance-resistance combination. In some cases, coil 16 can encircle acontainer 16a containing ionized fluid at a reference temperature.Preferably and advantageously, the components of the second tunedcircuit, which is designated by reference numeral 20, are of generallythe same magnitude as those of the tuned circuit 12. That is to say,coil 16 has substantially the same inductance as the coil 11, condenser19 has substantially the same capacitance as condenser 14, andresistance 18 has substantially the same ohmic value as resistance 13. AQ meter 21 is connected across the terminals of the coil 16 and it willbe understood that separate meters can be utilized or, alternatively,only one meter need be used, a suitable switching arrangement beingprovided to connect it alternately to the coils 11 and 16.

An oscillatory voltage is selectively applied to the tuned circuits 12,20 by an oscillator 23. To this end, one output terminal of theoscillator is grounded and the other output terminal is connectedthrough one gang 24a of a two gang, two position switch 24. The fixedterminals of switch gang 24a are connected, respectively, to thejunction between coil 11 and fixed resistance 13, and to the junctionbetween resistances 17, 18. In this manher, the output of the oscillatorappears across one of the fixed resistances 13 or 18, as determined bythe setting of switch 24, the circuit being completed through groundconnection 25 or 26. V i

The circuit also includes an amplifier 28, one terminal of the inputcircuit thereof being grounded and the other terminal being connectedthrough the second gang 24b of switch 24 either to condenser 14 of tunedcircuit 12 or condenser 19 of tuned circuit 20. In either case, thereturn circuit is completed through ground connection 25 or 26 so thatthe input circuit of the amplifier is connected in parallel withcondenser 14 or 19 depending upon the setting of the switch.

The output of amplifier 28 is fed to a squaring circuit 30, the outputvoltage of which varies as the square of the input voltage, as shown inthe copending application of D. R. de Boisblanc and R. S. Marsden,Serial No. 220,115, entitled Thermal Noise Thermometer, filed April 9,1951, now abandoned. The output voltage of squaring circuit can be readby a meter 31.

In the operation of the circuit, container has a fluid therein,preferably a gas, whose temperature is to be measured. Adjustments ofvariable resistor 17 and condenser 19 are made until the Q of circuit isequal to the Q" of tuned circuit 12, as noted by observation of themeters 15, 21. With the circuits in this condition, the temperature ofthe fluid in container 10 and the ambient temperature of the tunedcircuit 20 is proportional to the squares of the voltages appearing atthe terminals of switch gang 24b. The ambient temperature of circuit 20can be readily calcuated or, alternatively, it is within the scope ofthe invention to provide a second vessel 16a encircled by the coil 16containing a reference ionized iluid at a known temperature. Thereupon,readings are taken of meter 31 with the switch 24 in both positionswhereupon the temperature of the ionized fluid within container 10 canbe calculated readily from the relationship:

In a broader aspect of the invention, the tuned circuit 20 can beeliminated, the meter 31 being calibrated by successively passing gasstreams of the fluid whose tem perature is to be determined at a knownflow rate and at different temperatures through the vessel 10. Aftersuch calibration, the temperature ofsubsequent gas streams can be readdirectly from the meter 31.

Since ionized particles are present in flame zones, it will be evidentthat the apparatus can also be used to determine thetemperature orcondition of a flame zone which may be continuously or intermittentlypresent within the vessel 10. It will be evident, therefore, that I haveachieved the objects of my invention in providing an improved circuitfor determining the conditions of an ionized body of fluid and, inparticular, in measuring the temperature thereof.

The output of the coil 11 and its associated tuned circuit is affectedby the ambient temperature of the coil. However, the resistance of thecoil can be made sutficiently low so that the voltages arising from thissource are substantially less than 5 percent of the total voltagedeveloped by the circuit. Further, if the ambient temperaturefluctuations are not severe, they can be compensated for by calibrationso that the final measurement has an accuracy of better than 1 percent.In some applications, the temperature of coil 11 is regulated byoperating at slightly above the temperature of the fluid or by watercooling the coil.

The linear movement of the molecules in the gas flowing through vesselof pipe 10 also creates a signal which appears at the output of theresonant circuit. The voltage from this source is small compared to thevoltage representative of temperature and it decreases with increasingfrequency. At frequencies above 100 kilocycles' per second, themagnitude of the signal resulting from linear motion of the gasmolecules is vanishingly small.

While the invention has been described in connection with a present,preferred embodiment thereof, it is to be understood that thisdescription is illustrative only and is not intended to limit theinvention.

I claim:

1. 1n apparatus of the character described, a tuned circuit including aninductance coil, and a container encircled by said coil, an ionizedfluid in said container, an oscillator, a circuit for producing anoutput voltage which varies as the square of the input voltage, meansindicating said output voltage, and means for coupling said oscillatorand the input of said squaring circuit to said tuned circuit.

2. in apparatus of the character described, a tuned circuit including aninductance coil, and a container encircled by said coil, a second tunedcircuit including an adjustable resistance for varying the Q of thetuned circuit, a unit including an oscillator, a unit including acircuit for producing an output voltage which varies as the square ofthe input voltage, and means indicating said output voltage, and meansfor selectively coupling both of said units to said tuned circuits.

3. In apparatus of the character described, an inductance coil, acontainer encircled by said coil, a cendenser connected in parallel withsaid coil to form a tuned circuit, a second tuned circuit including acoil, an adjustable resistance connected in series therewith, and acondenser connected in parallel with the condenserresistancecombination, a unit including an oscillator, a unit including a circuitfor producing an output voltage which varies as the square of the inputvoltage, and means indicating said output voltage, and means forselectively coupling both of said units to said tuned circuits.

4. In apparatus of the character described, an inductance coil, acontainer encircled by said coil, a fixed resistance connected in serieswith said coil, and a condenser connected in parallel with thecoil-resistance unit, a second tuned circuit including a coil, anadjustable resistance and a fixed resistance connected in seriestherewith, and a condenser connected in parallel with thecondenser-resistance combination, a unit including an oscillator, a unitincluding a circuit for producing an output voltage which varies as thesquare of the inputv voltage, and means indicating said output voltage,and means for selectively coupling both of said units to said tunedcircuits.

5. In apparatus of the character described, an inductance coil, acontainer encircled by said coil, an ionized gas whose temperature is tobe measured in said container, a fixed resistance connected in serieswith said coil, and a condenser connected in parallel with thecoil-resistance unit, an oscillator, a circuit for producing an outputvoltage which varies as the square of the input voltage, meansindicating said output voltage, leads connecting said oscillator acrosssaid fixed resistance, and leads connecting the input of said squaringcircuit in parallel with said condenser.

6. In apparatus of the character described, an inductance coil, acontainer encircled by said coil, a fixed resistance connected in serieswith said coil, and a condenser connected in parallel with thecoil-resistance unit, means for'measuring the of said tuned circuit, asecond tuned circuit including a coil, an adjustable resistance and afixed resistance connected in series therewith, and a condenserconnected in parallel with the condenser-resistance combination, meansfor measuring the Q of said tuned circuit, a unit including anoscillator, aunit including a circuit for producing an output voltagewhich varies as the square of the input voltage, and means indicatingsaid output voltage, and means for selectively coupling both of saidunits to said tuned circuits.

7. In apparatus of the character described, a tuned circuit including aninductance coil, a container encircled by said coil, a fixed resistanceconnected in series with said coil, and a condenser connected inparallel with the coil-resistance unit, a second tuned circuit includinga coil, an adjustable resistance and a fixed resistance con nected inseries therewith, and a condenser connected in parallel with thecondenser-resistance combination, a two gang switch, an oscillatorconnectible through one gang of said switch so as to apply anoscillatory voltage across the fixed resistance of one tuned circuitwith the switch in a first position and to apply said oscillatoryvoltage across the fixed resistance of the other tuned circuit with theswitch in a second position, an amplifier having an input circuit and anoutput circuit, said input circuit being connectible through the othergang of said switch across the condenser of said one tuned circuit withthe switch in said first position and being connected across thecondenser of said other tuned circuit with the switch in said secondposition, a squaring circuit coupled to the output circuit of saidamplifier, said squaring circuit producing an output voltage whichvaries as the square of the input voltage, and means indicating theoutput voltage of said squaring circuit.

8. In apparatus for measuring the temperature of a fluid, a container,an ionized fluid in said container, an inductance coil encircling saidcontainer, a tuned circuit including said coil as one element thereof, asecond tuned circuit having an adjustable resistance for varying the Qof said circuits, means for supplying an oscillatory voltage to saidcircuits, a circuit for producing an output voltage which varies as thesquare of the input voltage applied thereto, means indicating saidoutput voltage, and means selectively coupling said squaring circuit tosaid tuned circuits.

9. In apparatus for measuring the temperature of a fluid, a container,an ionized fluid in said container, an inductance coil encircling saidcontainer, a tuned circuit including said coil as one element thereof, asecond tuned circuit having an adjustable resistance for varying the Qof said circuits, and an inductance coil,,a container for a referencefluid encircled by said second coil, means for supplying an oscillatoryvoltage to said circuits, a circuit for producing an output voltagewhich varies as the square of the input voltage applied thereto, meansindicating said output voltage, and means selectively coupling saidsquaring circuit to said tuned circuits.

10. In apparatus for measuring the temperature of a fluid, a container,an ionized fluid in said container, an inductance coil encircling saidcontainer, a tuned circuit including said inductance coil, a fixedresistance connected in series with said coil, and a condenser connectedin parallel with the coil-resistance unit, a second tuned circuitincluding a coil, an adjustable resistance and a fixed resistanceconnected in series therewith, and a condenser connected in parallelwith the condenserresistance combination, a two gang switch, anoscillator connectible through one gang of said switch so as to apply anoscillatory voltage across the fixed resistance of one tuned circuitwith the switch in a first position and to apply said oscillatoryvoltage across the fixed resistance of the other tuned circuit with theswitch in a second position, an amplifier having an input circuit and anoutput circuit, said input circuit being connected through the othergang of said switch across the condenser of said one tuned circuit withthe switch in said first position and being connected across thecondenser of said other tuned circuit with the switch in said secondposition, a squaring circuit coupled to the output circuit of saidamplifier, said squaring circuit producing an output voltage whichvaries as the square of the input voltage, and means indicating theoutput voltage of said squaring circuit.

11. In apparatus for measuring the temperature of a fluid, a container,an ionized fluid in said container, an inductance coil encircling saidcontainer, a condenser connected in parallel with said coil to form atuned circuit, a second tuned circuit including a coil, an adjustableresistance connected in series therewith, and a condenser connected inparallel with the coil-resistance combination, the Q or" said firstmentioned tuned circuit being equal to the Q of said second tunedcircuit with the result that the ratio of the squares of the voltagesappearing across said tuned circuits is equal to the ratio of thethermal noise voltages in the respective coils, the thermal noisevoltage of said inductance coil being representative of the ionizationof fluid encompassed thereby, a unit including an oscillator and apotential measuring device, and means for selectively connecting saidunit to said tuned circuits.

12. In apparatus for measuring the temperature of a fluid, a container,an ionized fluid in said container, an inductance coil encircling saidcontainer, a tuned circuit including said coil as one element thereof, asecond tuned circuit having an adjustable resistance, means forsupplying an oscillatory voltage to said circuits, a circuit forproducing an output voltage which varies as to the square of the inputvoltage applied thereto, means indicating said output Voltage, and meansselectively-coupling said squaring circuit to said tuned circuits, the Qof said first mentioned tuned circuit being equal to the Q of saidsecond tuned circuit with the result that the ratio of the squares ofthe voltages appearing across said tuned circuits is equal to the ratioof the thermal noise voltages in the respective coils, the thermal noisevoltage of said inductance coil being representative of the ionizationof fluid encompassed thereby.

References Cited in the file of this patent UNITED STATES PATENTS1,610,971 Ruben Dec. 14, 1926 2,482,773 Hieronymus Sept. 27, 19492,485,931 Slonczewski Oct. 25, 1949 2,572,908 Brcnholdt Oct. 30, 19512,587,631 Kuehne Mar. 4, 1952 OTHER REFERENCES Review of ScientificInstruments, May 1949, volume 20, No. 5, pages 349-352, Article byCalcote.

